1. Field of the Invention
This application is related to the commonly assigned U.S. application Ser. No. 08/591,299, which was filed on Jan. 25, 1996, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to a light phase modulating device used in an optical data recording and reproducing apparatus, such as a magneto-optic disc apparatus, and the optical data recording and reproducing apparatus.
2. Description of Related Art
In a magneto-optic disc apparatus, data magnetically recorded on a magneto-optic disc (recording medium) is reproduced by making linearly polarized light incident upon the recording medium and detecting a slight change in the state of the polarization of the signal light reflected by the recording medium. However, the phase of the reflected light is subject to a modulation due to either the phase of the incident laser beams being unstable, disturbance, temperature/humidity, or an irregular thickness of the recording disc, etc., and hence the S/N (signal-to-noise ratio) of the signal to be reproduced deteriorates.
To prevent deterioration of the S/N, in the prior art, the optical elements of the apparatus are produced and assembled as precisely as possible. However, due to this required strict precision, production, assembly and adjustment require a long time and are costly.